Dynamic Channel Assignment with Cumulative Cochannel Interference |
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This paper (paper_dca_04.pdf ) studies dynamic channel assignment (DCA) for wireless cellular systems under space and time-varying channel demand. The DCA problem treated here is to minimize the number of channels required to satisfy demand while also satisfying cochannel interference constraints. Unlike DCA work that allows two base stations to use the same channel if their geographic separation exceeds a reuse distance, here cumulative cochannel interference constraints govern channel reuse. These use a threshold decision criterion based on the carrier-to-interference ratio. The paper has two contributions. First, it provides an empirical bound on the difference between the minimal number of channels required in the reuse distance case versus the cumulative interference case in the context of linearly increasing demand. The bound is characterized using only reuse distance. To establish the bound it uses an Integer Programming (IP) based strategy that uses some channel assignments for one demand state to assign channels for the next state. The impact of cumulative interference constraints is observed to be very small for small geographic localities. Second, the paper proposes a new, fast DCA heuristic whose design is based on characterizing channel reuse patterns used by the IP-based strategy. The number of channels used by the heuristic under a zero blocking condition is comparable for both the heuristic and the IP-based strategy under linearly increasing demand. The performance of this heuristic is also examined for call arrivals modeled by a two state discrete-time Markov chain and a uniform distribution of holding times. |
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